media: set proper max seg size for devices on Exynos SoCs

All multimedia devices found on Exynos SoCs support only contiguous
buffers, so set DMA max segment size to DMA_BIT_MASK(32) to let memory
allocator to correctly create contiguous memory mappings.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>